Differential signal transmission circuit and vehicle electronic system thereof

Abstract

A differential signal transmitting circuit and its automotive electronic system are disclosed. The differential signal transmitting circuit includes a differential signal bridge circuit, a first current source circuit, a second current source circuit, an amplitude control circuit, and a common-mode control circuit. The first current source circuit provides a first current based on a first current control signal. The second current source circuit receives a second current from a second node based on a second current control signal. The differential signal bridge circuit is coupled between the first and second current source circuits to provide a pair of output differential signals based on a pair of input differential signals and to provide a common-mode voltage. The amplitude control circuit provides a first current control signal based on a pair of output differential signals. The common-mode control circuit provides a second current control signal based on the common-mode voltage.

Claims

1. A differential signal transmitting circuit, comprising: A first current source circuit receives a first current control signal to provide a first fixed current and a first regulated current to a first node; A second current source circuit receives a second current control signal to receive a second fixed current and a second adjustable current from a second node; a first P-type transistor has a first terminal coupled to the first node, a control terminal receiving a first input differential signal from a pair of input differential signals, and a second terminal providing a first output differential signal from a pair of output differential signals; a first N-type transistor has a first terminal coupled to the second terminal of the first P-type transistor, a control terminal receiving the first input differential signal, and a second terminal coupled to the second node; a second P-type transistor has a first terminal coupled to the first node, a control terminal receiving a second input differential signal from the pair of input differential signals, and a second terminal providing a second output differential signal from the pair of output differential signals; a second N-type transistor has a first terminal coupled to the second terminal of the second P-type transistor, a control terminal receiving the second input differential signal, and a second terminal coupled to the second node; A first resistor is coupled between the second terminal of the first P-type transistor and the second terminal of the second P-type transistor; a second resistor and a third resistor are connected in series between the second terminal of the first P-type transistor and the second terminal of the second P-type transistor, wherein a connection point of the second resistor and the third resistor provides a common-mode voltage. An amplitude control circuit receives a first input signal, the first input differential signal, the first output differential signal, and the second output differential signal to determine whether the amplitude of the pair of output differential signals corresponds to the first input signal, and correspondingly provides the first current control signal to the first current source circuit; and a common-mode control circuit receives a second input signal and the common-mode voltage to provide the second current control signal to the second current source circuit based on whether the common-mode voltage corresponds to the second input signal.

2. The differential signal transmitting circuit as claimed in claim 1, wherein the amplitude control circuit comprises: A multiplexer circuit receives the first input differential signal, the first output differential signal, and the second output differential signal to provide one of the first output differential signal and the second output differential signal based on the first input differential signal; a sampling circuit is coupled to the multiplexer circuit to sample the one of the first output differential signal and the second output differential signal and provide an amplitude voltage. A first voltage source receives the first input signal to provide an amplitude reference voltage; a first error amplifier receives the amplitude voltage and the amplitude reference voltage to provide the first current control signal.

3. The differential signal transmitting circuit as claimed in claim 2, wherein the first voltage source includes a bandgap reference circuit.

4. The differential signal transmitting circuit as claimed in claim 2, wherein the amplitude control circuit further includes a unity-gain amplifier coupled between the multiplexer circuit and the sampling circuit to buffer one of the first output differential signal and the second output differential signal provided by the multiplexer circuit.

5. The differential signal transmitting circuit as claimed in claim 1, wherein the common-mode control circuit comprises: A second voltage source receives the second input signal to provide a common-mode reference voltage; A second error amplifier receives the common-mode voltage and the common-mode reference voltage to provide the second current control signal.

6. The differential signal transmitting circuit as claimed in claim 5, wherein the second voltage source includes a bandgap reference circuit.

7. The differential signal transmitting circuit as claimed in claim 1, wherein the first current source circuit comprises: A first current source provides the first fixed current; And a third P-type transistor having a first terminal coupled to a high voltage of a system, a control terminal for receiving the first current control signal, and a second terminal for providing the first regulating current.

8. The differential signal transmitting circuit as claimed in claim 1, wherein the second current source circuit comprises: A second current source receives the second fixed current; And a third N-type transistor having a first terminal for receiving the second regulating current, a control terminal for receiving the second current control signal, and a second terminal coupled to a ground voltage.

9. A vehicle electronic system, comprising: A vehicle-mounted unit includes a differential signal transmitting circuit as described in claim 1, for transmitting display data and a display control signal via the pair of output differential signals; And a vehicle display device having a display panel, a display driving circuit, and a differential signal receiving circuit, wherein the differential signal receiving circuit is used to receive display data and display control signals from the vehicle host, and the display driving circuit drives the display panel to display based on the display data and display control signals provided by the differential signal receiving circuit.

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